Although there is considerable interest in immunity to schistosomiasis, few antigens have been well characterized and little progress has been made in isolating stage-specific or species-specific antigens in purified form. Attempts to immunize animals with crude extracts of worm material have met with only limited success. In this regard, purified fractions of surface antigens might be more efficacious as a potential vaccine. In addition, purified fractions of surface antigens could be used to produce monoclonal antibodies from hybridomas. Such antibodies would facilitate further antigen isolation and lead to the development of ELISA for circulating antigens. Thorough characterization of tegumental surface chemistry is a necessary first step to any of these applications. I. Surface antigens of adult S. mansoni will continue to be characterized using several direct and metabolic labeling methods. II. Surface antigens from adult worms will be compared with those from cercariae and several stages of schistosomula. III. Individual antigens will be isolated and purified. IV. Purified antigens will be used for improved serodiagnosis and for possible protection against murine schistosomiasis. V. Hybridoma technology will be used to produce monoclonal antibodies.